Nonmagnetic Elinvar-Type Alloys in the Mn–Cu–Ni System

Abstract

Measurements of Young’s modulus at −150∼400°C and of rigidity modulus and hardness at room temperature have been carried out for Mn–Cu–Ni alloys subjected to various conditions of heat treatment and cold working. A distinct Néel point appears in the Young’s modulus vs temperature curves for the ternary alloys containing 5.06∼55.16% copper and 4.08∼25.35% nickel when heated at 950°C for 1 hr and then slowly cooled. Young’s modulus at room temperature in the state of annealing are higher than those in the state of cold working or water quenching, and the difference between the two becomes prominent as the manganese and nickel contents increased. The temperature coefficient of Young’s modulus is remarkably varied by annealing, cold working, water quenching and reheating after cold working or water quenching. It is also to be noted that the temperature coefficient shows a marked variation with composition. The presence of a large positive maximum in the temperature coefficients vs composition curve indicates the Elinvar property of the alloys. The rigidity modulus and its temperature coefficient at room temperature show a similar variation with process of heat treatment, cold reduction rate and composition to Young’s modulus and its temperature coefficients. The hardness in the state of reheating after cold working or water quenching is higher than that in the state of annealing, cold working or water quenching. Corrosion resistivity of those Elinvar type alloys is fairly large.